Synthesis of borophene nanoribbons on Ag(110) surface

We present the successful synthesis of single-atom-thick borophene nanoribbons (BNRs) by self-assembly of boron on Ag(110) surface. The scanning tunneling microscopy (STM) studies reveal high quality BNRs: all the ribbons are along the $[\ensuremath{-}110]$ direction of Ag(110), and can run across the steps on the surface. The width of ribbons is distributed in a narrow range around $10.3\ifmmode\pm\else\textpm\fi{}0.2\phantom{\rule{0.16em}{0ex}}\mathrm{nm}$. High resolution STM images revealed four ordered surface structures in BNRs. Combined with DFT calculations, we found that all four structures of boron nanoribbons consist of the boron chains with different widths, separated by hexagonal hole arrays. The successful synthesis of BNRs enriches the low dimensional allotrope of boron and may promote further applications of borophene.